Such circuits are used for example in radar sensors for motor vehicles in order to produce and/or process the radar signals. The high-frequency component is typically an integrated semiconductor component (MMIC, or Monolithic Microwave Integrated Circuit) that is encapsulated in a housing suitable for surface-mounting technique, for example an eWLB (embedded Wafer Level Ball Grid) housing. The fastening and electrical contacting of the high-frequency component on the circuit board takes place for example using spherical solder contacts. Via these contacts, both low-frequency signals used for power supply and to control the component and also the actual high-frequency signals are transmitted.
The object of the present invention is to create a circuit for millimeter wave signals that can be produced more easily.
According to the present invention, this object is achieved in that the housing forms, on at least one housing wall facing away from the circuit board, a coupling structure for the millimeter wave signals, to which a hollow conductor is coupled outside the housing.
According to the present invention, in this way the millimeter wave signals are coupled in and/or out immediately through the wall of the housing, bypassing the galvanic contacts on the side facing the circuit board.
This solution has the advantage that a high-frequency-capable substrate is no longer required for the circuit board, thus saving costs. Because the galvanic contacts are then used only to transmit low-frequency signals, they also no longer need be high-frequency-capable, so that larger production tolerances can be permitted, thus achieving further savings.
The term “hollow conductor” is also used here for hollow conductor structures whose hollow space contains a dielectric.
The housing wall on which the coupling structure is formed can be a side wall of the housing that is oriented at a right angle to the circuit board, or preferably can be the housing wall parallel to the circuit board on the side opposite the circuit board.
The coupling structure in the housing is preferably formed by a wave conductor that can be filled with a dielectric and that is realized in such a way that it conducts the millimeter waves to the housing wall and couples them out through this wall, so that further conducting can then take place via the hollow conductor situated outside the housing. Preferably, for this purpose the hollow conductor has, at its end adjacent to the housing, an adapting structure that provides a strong and largely impact-free coupling between the housing and a hollow conductor.
In an advantageous specific embodiment, the hollow conductor is formed in a hood that covers the housing and that can be mounted on the circuit board independently of the housing. This hood can at the same time form a wave trap that enables a reduction of the insertion loss. A plurality of coupling points for a plurality of hollow conductors can be formed on one and the same housing. In this case, at the same time the mentioned wave traps improve the insulation of the plurality of coupling points from one another.